diff --git a/contrib/amcheck/verify_nbtree.c b/contrib/amcheck/verify_nbtree.c
index c7cd8d3f043..5d98d8a2ad3 100644
--- a/contrib/amcheck/verify_nbtree.c
+++ b/contrib/amcheck/verify_nbtree.c
@@ -33,7 +33,6 @@
 #include "verify_common.h"
 #include "catalog/index.h"
 #include "catalog/pg_am.h"
-#include "catalog/pg_opfamily_d.h"
 #include "common/pg_prng.h"
 #include "lib/bloomfilter.h"
 #include "miscadmin.h"
@@ -329,24 +328,10 @@ bt_index_check_callback(Relation indrel, Relation heaprel, void *state, bool rea
 				 errmsg("index \"%s\" metapage has equalimage field set on unsupported nbtree version",
 						RelationGetRelationName(indrel))));
 	if (allequalimage && !_bt_allequalimage(indrel, false))
-	{
-		bool		has_interval_ops = false;
-
-		for (int i = 0; i < IndexRelationGetNumberOfKeyAttributes(indrel); i++)
-			if (indrel->rd_opfamily[i] == INTERVAL_BTREE_FAM_OID)
-			{
-				has_interval_ops = true;
-				break;
-			}
-
 		ereport(ERROR,
 				(errcode(ERRCODE_INDEX_CORRUPTED),
 				 errmsg("index \"%s\" metapage incorrectly indicates that deduplication is safe",
-						RelationGetRelationName(indrel)),
-				 has_interval_ops
-				 ? errhint("This is known of \"interval\" indexes last built on a version predating 2023-11.")
-				 : 0));
-	}
+						RelationGetRelationName(indrel))));
 
 	/* Check index, possibly against table it is an index on */
 	bt_check_every_level(indrel, heaprel, heapkeyspace, readonly,
diff --git a/doc/src/sgml/btree.sgml b/doc/src/sgml/btree.sgml
index 027361f20bb..3eef5202c56 100644
--- a/doc/src/sgml/btree.sgml
+++ b/doc/src/sgml/btree.sgml
@@ -875,10 +875,18 @@ options(<replaceable>relopts</replaceable> <type>local_relopts *</type>) returns
    <itemizedlist>
     <listitem>
      <para>
-      <type>text</type>, <type>varchar</type>, and <type>char</type>
-      cannot use deduplication when a
-      <emphasis>nondeterministic</emphasis> collation is used.  Case
-      and accent differences must be preserved among equal datums.
+      <type>text</type> and <type>varchar</type> cannot use deduplication when
+      a <emphasis>nondeterministic</emphasis> collation is used.  Case and
+      accent differences must be preserved among equal datums.
+     </para>
+    </listitem>
+
+    <listitem>
+     <para>
+      <type>character</type> (and its aliases <type>char</type> and
+      <type>bpchar</type>) cannot use deduplication.  Trailing spaces are
+      disregarded when comparing two values, but must be preserved among
+      equal datums.
      </para>
     </listitem>
 
diff --git a/src/backend/utils/adt/datum.c b/src/backend/utils/adt/datum.c
index 5aab1edb7bc..2e906add921 100644
--- a/src/backend/utils/adt/datum.c
+++ b/src/backend/utils/adt/datum.c
@@ -43,6 +43,7 @@
 #include "postgres.h"
 
 #include "access/detoast.h"
+#include "catalog/pg_type_d.h"
 #include "common/hashfn.h"
 #include "fmgr.h"
 #include "utils/datum.h"
@@ -421,20 +422,17 @@ datum_image_hash(Datum value, bool typByVal, int typLen)
  * datum_image_eq() in all cases can use this as their "equalimage" support
  * function.
  *
- * Currently, we unconditionally assume that any B-Tree operator class that
- * registers btequalimage as its support function 4 must be able to safely use
- * optimizations like deduplication (i.e. we return true unconditionally).  If
- * it ever proved necessary to rescind support for an operator class, we could
- * do that in a targeted fashion by doing something with the opcintype
- * argument.
+ * Earlier minor releases erroneously associated this function with
+ * bpchar_pattern_ops.  Detect that case to rescind deduplication support,
+ * without requiring initdb.
  *-------------------------------------------------------------------------
  */
 Datum
 btequalimage(PG_FUNCTION_ARGS)
 {
-	/* Oid		opcintype = PG_GETARG_OID(0); */
+	Oid			opcintype = PG_GETARG_OID(0);
 
-	PG_RETURN_BOOL(true);
+	PG_RETURN_BOOL(opcintype != BPCHAROID);
 }
 
 /*-------------------------------------------------------------------------
diff --git a/src/backend/utils/adt/varlena.c b/src/backend/utils/adt/varlena.c
index 63662e3f779..51f6ab0960f 100644
--- a/src/backend/utils/adt/varlena.c
+++ b/src/backend/utils/adt/varlena.c
@@ -2655,16 +2655,23 @@ varstr_abbrev_abort(int memtupcount, SortSupport ssup)
 /*
  * Generic equalimage support function for character type's operator classes.
  * Disables the use of deduplication with nondeterministic collations.
+ *
+ * Earlier minor releases erroneously associated this function with
+ * bpchar_ops.  Detect that case to rescind deduplication support, without
+ * requiring initdb.
  */
 Datum
 btvarstrequalimage(PG_FUNCTION_ARGS)
 {
-	/* Oid		opcintype = PG_GETARG_OID(0); */
+	Oid			opcintype = PG_GETARG_OID(0);
 	Oid			collid = PG_GET_COLLATION();
 	pg_locale_t locale;
 
 	check_collation_set(collid);
 
+	if (opcintype == BPCHAROID)
+		PG_RETURN_BOOL(false);
+
 	locale = pg_newlocale_from_collation(collid);
 
 	PG_RETURN_BOOL(locale->deterministic);
diff --git a/src/test/regress/expected/btree_index.out b/src/test/regress/expected/btree_index.out
index 21dc9b5783a..9fb4529b0c6 100644
--- a/src/test/regress/expected/btree_index.out
+++ b/src/test/regress/expected/btree_index.out
@@ -608,8 +608,6 @@ select * from btree_bpchar where f1::bpchar like 'foo%';
  fool
 (2 rows)
 
--- get test coverage for "single value" deduplication strategy:
-insert into btree_bpchar select 'foo' from generate_series(1,1500);
 --
 -- Perform unique checking, with and without the use of deduplication
 --
diff --git a/src/test/regress/sql/btree_index.sql b/src/test/regress/sql/btree_index.sql
index 6aaaa386abc..4d862130ffb 100644
--- a/src/test/regress/sql/btree_index.sql
+++ b/src/test/regress/sql/btree_index.sql
@@ -326,9 +326,6 @@ explain (costs off)
 select * from btree_bpchar where f1::bpchar like 'foo%';
 select * from btree_bpchar where f1::bpchar like 'foo%';
 
--- get test coverage for "single value" deduplication strategy:
-insert into btree_bpchar select 'foo' from generate_series(1,1500);
-
 --
 -- Perform unique checking, with and without the use of deduplication
 --